Bad news for endurance athletes

Footballers’ joints and runners’ bones
A British research team was stunned to discover that the prevalence of osteoarthritis (OA) of the hips in ex-pro footballers was 10 times higher than that of age-matched controls – even though none of the ex-players were aware of suffering hip injuries during their playing careers.

Of 68 ex-players who responded to a questionnaire survey, nine (13.24%) reported having OA of the hip, and six of these had undergone eight total hip replacements. By contrast, only two (1.47%) of 136 controls showed evidence of OA, and none had needed hip replacements.

The researchers would have expected the ex-players with hip problems to have suffered hip injuries during their careers, especially since osteoarthritis of the knee is known to be linked with previous surgery or injury. Why the difference? The researchers speculate that minor hip joint injuries may be harder to detect, with some masquerading as groin problems.

Another home research team was amazed to find a negative association between long distance running and bone mineral density. This counter-intuitive finding is probably connected with the relatively low forces applied to the limbs during running – particularly over long distances.

The researchers point out: ‘Athletes involved in sports and training where forces applied to the limbs are in excess of 10 times body weight (gymnastics, weightlifting and volleyball) have been found to have higher [bone mineral density] than those involved in sports where forces are only in the range of 5-10 times body weight, such as endurance running’.

It seems that, although running includes many more cycles of foot strike than these other sports, the lower loads are less stimulatory to bone accretion. This would be particularly true of distance running which is associated with lower intensities and thus lower forces applied to the limbs.